3.1 The ecosystem impact of bottom
trawling

3.1.1
Introduction

Bottom trawling fleets predominate in many Mediterranean
fisheries, being responsible for a high share of total catches and, in many
cases, yielding the highest earnings among all the fishing sub-sectors. The high
profitability of this fishing practice is largely due to its low selectivity
with respect to sizes and species caught, and to the high harvests generated.
Trawlers have dramatic effects on the ecosystem including physical damage to the
seabed and the degradation of associated communities, the overfishing of
demersal resources, and the changes in the structure and functioning of marine
ecosystems derived from the depletion of populations and the huge amount of
bycatches and associated discards.

3.1.2 Overview

Whilst the problems related to the impact of bottom trawling
on Posidonia beds and soft bottoms have been dealt with elsewhere in this
report, the present section focuses on the ecosystem effects of trawling derived
from its low selectivity and the issues relating to the capture of undersized
individuals and discarding. Bycatches (and subsequent discards) of particularly
vulnerable species or groups are covered in other parts of this report, as are
the effects of trawl discards on marine seabird populations. The ecosystem
effects of discards reported below refer to demersal communities.

3.1.3 Size selectivity on
commercial species

Bottom trawling fisheries in the Mediterranean are essentially
multispecies. Monospecific fisheries are very rare and are largely limited to
deep shrimp fisheries on muddy slope bottoms. The high marketability of small
fish in many countries encourages the targeting of the juvenile fraction of some
species, often in violation of laws regarding minimum sizes. Demersal
populations are consequently overfished, shallow areas (within the three-mile
coastal limit or on bottoms less than 50 m deep, depending on the country) are
illegally trawled and small, illegal mesh sizes are used. Examples are
widespread throughout the Mediterranean and are not detailed here since they
mostly concern recurring issues related to classical fisheries management. The
well-known massive seasonal harvest of undersized red mullet, which are caught
on shallow grounds when they settle, is though worth mentioning. The
paradigmatic case of the hake fishery using bottom longlines and otter trawling
gears in the Gulf of Lions also deserves highlighting. Data from the late 1980s
clearly showed that the trawling fishery exploited the juvenile fraction of the
population since the mean size of catches was only 17.9 cm, which strongly
contrasted with the 48.2 cm corresponding to longline catches (Lleonart,
1990).

Information on discards in Mediterranean trawl fisheries
confirm the magnitude of the problem, though they vary considerably in amount
and composition depending on region, boat size, season, bottom type and depth of
the exploited ground. The first regional study addressing the magnitude of
discards in the western Mediterranean involved the monitoring of fishing fleets
in seven ports (six Spanish and one Italian). Combined data gave discard
estimations ranging from 23-67% of total catch in bottoms less than 150 m deep,
13-62% in bottoms 150 to 350 m deep and 14-43% in slope bottoms deeper than 350
m (Carbonell, 1997; Carbonell, Martin and de Ranieri, 1998). Data from a single
locality, the Catalan port of Vilanova i la Geltru (north-west Mediterranean),
illustrate this high quantitative variability. Monitoring of the fleet there
revealed that the annual average of discards ranged between 13% and 39% of the
total catch for small boats (< 150 hp) and between 17% and 48% for larger
boats (> 150 hp), depending on the depths exploited. The amount discarded,
however, peaked at 75.4% and 66.6%, respectively, in the case of larger boats
operating in spring and smaller ones operating in the summer on shelf bottoms
(< 150-m depth).

Similar high discard levels have been reported for other
Mediterranean trawl fisheries. Total annual discards in Sicily during the 1980s
were estimated at around 70 000 t, accounting for an average of 44-72% of
catches (Charbonnier, 1990). The monitoring of fleets operating in three major
Greek fishing grounds (Ionian Sea, Cyclades Islands and Thracian Sea) during
1988-1997 yielded discard estimations of 40%, 55% and 25% of the total catch of
fish, crustaceans and cephalopods, respectively (Machias et al., 1999).
Field studies carried out in 1995 showed that the fraction discarded by the
trawl fleet operating in the Cyclades area, in the Aegean Sea, amounted to 59%
of the total catch in bottoms less than 150 m deep, 63% in bottoms 150-200 m
deep, and 37% in grounds deeper than 300 m (Vassilopoulou and Papaconstantinou,
1998). On the whole, discards in the Hellenic commercial trawl fishery are
estimated to account for 45% of total catch (Stergiou et al., 1998). The
rapido beam trawler fleet (56 units) based in Chioggia in the
Adriatic Sea produces qualitatively heterogeneous discards depending on the
species target. Whilst pectinid fishing involves the exploitation of sandy
bottoms offshore and discards consist of echinoderms (32% in weight),
crustaceans (26%), molluscs (23%) and porifers (15%), flatfish fishing is
carried out on muddy coastal areas, where molluscs and crustaceans account for
the bulk of discards (60% and 30%, respectively).

High discard levels are also common in the case of
Mediterranean deep sea trawling fisheries. Discards by the trawling fleet
operating on the upper slope (230-611 m) off Alacant (south-east Spain) have
been estimated at 34.6% of the total catch (Soriano and Sánchez-Lizaso,
2000). The low selectivity of trawling is highlighted by data from this fishery
showing that up to 95 species are taken; only 12 of these account for nearly 89%
of the total, and 89 of them are discarded. The analysis of discards in the
Norway lobster (Nephrops norvegicus) and red shimp (Aristeus
antennatus) fisheries at 280-720 m in the Balearic Islands (western
Mediterranean), estimated at an average of 42% of the total catch, led the
authors to conclude that an important fraction of the catch of the two
deep-sea decapod crustacean fisheries of the Western Mediterranean is
discarded (Moranta, Massutí and Morales-Nin, 2000). Longer tows, to
compensate for the reduced biomass, seem to result in lower selectivity by the
mesh and higher discard rates.

Discarding can also involve important commercial species,
especially smallest size classes. Discards of commercial species in Greek waters
are reported to range from 0% for red mullet (Mullus surmuletus) to 10%
for hake (Merluccius merluccius) and shrimp Parapenaeus
longirostris (Machias et al., 1999). The bulk of discards (66%) in
the Balearic deep sea crustacean fisheries at a depth of 300 m referred to above
correspond to undersized marketable species. The study of hake discards
(Merluccius merluccius), forkbeard (Phycis blenoides) and poor cod
(Trisopterus minutus capelanus) in the trawl fishery of the northern
Tyrrhenian Sea revealed that they can reach high levels, depending on the
species, the season and the depth exploited (Sartor et al., 1999).
Maximum estimates of discards were 34.1% of total catch (in weight) for hake,
41% for forkbeard and 39% for poor cod, whereas total annual mean discards in
the traditional trawl fishery amounted to 39%, 65% and 57% respectively in
numbers of individuals. All individuals under 10 cm are discarded in all three
species.

Although a proportion of discards in Mediterranean trawling
fisheries may survive, few helpful data on which to base quantitative estimates
exist. Observations derived from experiments on aquaria carried out on board
point to the low mortality of crustaceans caught as a bycatch in Catalan trawl
fisheries, whereas survival rates of fish are highly heterogeneous and vary
strongly according to the species (i.e. 0% for Trachurus spp. and 100% in
Scyliorhinus canicula) (Sánchez, 2000). Another study of bycatch
survival in the rapido fleet operating in the northern Adriatic
showed low mortality in all taxa examined during the three to four hours
following capture (Pranovi et al., 1999).

3.1.5 Impact of discards on
demersal ecosystems

The impact of discards goes far beyond single-species
demographic effects, since discarded biomass can alter ecosystem structure by
favouring scavengers (Moranta, Massutí and Morales-Nin, 2000). The
consequences of the fishing-driven increase in food supply stemming from have
seldom been addressed by specific studies.

The only work dealing with this issue in the Mediterranean is
based on photographic surveys carried out off the Catalan coast in the
northwestern Mediterranean, and focuses on the estimation of the consumption
rate of fishery discards by scavengers (Bozzano and Sardà, 2002). The
study used a baited camera, which was set on the sea floor at a depth of 100 and
300 m in two areas subjected to trawling with continual discards. Eight fish and
nine crustacean species were recorded feeding on the baits, and the benthic
snake eel Ophichthus rufus was the main scavenger species, followed by
isopods (i.e. Cyrolana borealis) and amphipods (i.e.
Schopelocheirushopei). Sporadic scavenging behaviour was even
reported for common fish species such as Spicara spp. and
Trachurus spp. Discarded material seems to enter demersal food webs quite
quickly, as suggested by the high consumption rates recorded. In all cases baits
were fully consumed within 24 hours, and consumption rates reached maximum
levels in deep bottoms at night. The authors concluded that the prevalence of
O. rufus indicated an environment dominated by a monospecific scavenger
guild, whose competitors and predators have probably been eliminated by fishing
activity. This conclusion is particularly interesting since it highlights the
multiple effects of fishing on complex systems such are communities and
ecosystems: fishing can favour a single species within the demersal ecosystem by
both removing its competitors and independently increasing its food availability
through discards.

3.1.6 Conclusions

There is compelling evidence that discards by Mediterranean
unselective trawling fleets are significant. The effect on marine communities is
twofold: at a single-species level, the population dynamics of a species are
altered, and at the ecosystem level profound changes occur because of the
disruption of food webs. Ecosystem modifications are triggered by the change in
the biomass and demographic structure of the different species as well as by the
increasing food supply for scavenger and opportunistic species. It is worth
noting that the latter can result in the trophic connection of separate
sub-systems (i.e. pelagic and benthic), making ecosystem consequences even more
dramatic.

Although bottom trawling is inherently rather unselective,
bycatches and discards can be minimized. Trawling can be limited and technical
measures can be introduced to improve selectivity. Trawl selectivity within an
area depends on many factors, ranging from the depth exploited or the kind of
bottom, to the season. Most impacting scenarios could be avoided by restricting
trawling both spatially and temporally. In this context, current provisions
banning trawling in coastal waters less than 50 m deep or three miles offshore
should be enforced effectively. Trawling gears could be made more selective by
using higher mesh sizes or incorporating special excluding devices, such as
those based on rigid grids. The former solution may be difficult to apply in
Mediterranean waters for social and political reasons, but the development and
compulsory use of excluding devices increasing selectivity (such as those in use
in some North Atlantic waters) deserve attention. Alternatively, the use of a
square mesh can also improve selectivity. It is convenient to mention here that
shorter trawling hauls are known to reduce discard rates (Stergiou et
al., 1998, Moranta, Massutí and Morales-Nin, 2000).

Partial solutions and technical improvements notwithstanding,
the banning of bottom trawling in large marine protected areas throughout the
Mediterranean Basin appears to be the only way of maintaining a sample set of
demersal ecosystems free of the damage caused by this widespread fishing
practice. These areas would moreover be very useful as a basic reference guide
to healthy bottom communities in the context of a future ecosystem-based
management of Mediterranean fisheries.

3.2 The impact of longlining on large
pelagic populations

3.2.1
Introduction

Pelagic longlining in Mediterranean waters inflicts
considerable mortality on elasmobranchs, marine turtles and seabirds taken as
bycatch or even (in the case of the former) target species. It is obvious,
however, that large pelagics, the objective of this fishery, is the group most
impacted by this gear. The main species targeted in the Mediterranean are
swordfish (Xiphias gladius), bluefin tuna (Thunnus thynnus) and to
a lesser extent, albacore (Thunnus alalunga). Bluefin tuna and swordfish
are exceptional in the Mediterranean context for being the only species whose
populations are subjected to an international TAC-based management regime. The
overall issue of the sustainable management of their populations is beyond the
scope of this report, and the discussion below focuses instead on the
selectivity of surface longline fisheries operating in Mediterranean waters as
it affects the immature, small-sized fraction of their dwindling populations and
the degree of compliance with current international legislation.

3.2.2 Overview. Brief summary of
the main fleets and fishing grounds

A variety of medium-scale and industrial pelagic longlining
fleets operate in Mediterranean waters, ranging from local coastal state fleets
to large industrial foreign fleets, whether Japanese, flag of convenience (FoC),
or even unflagged pirate fleets. FoC and pirate fleets are estimated
at about 100 units (GFCM, 1997). Surface longline gears, including those used by
local Mediterranean fleets, are deployed in large areas since line lengths of
50-60 km (bearing several thousand hooks) are not rare. Longline fleets in quest
of their highly migratory target fish species, even local ones, are highly
mobile, covering virtually the whole Mediterranean basin. A significant share of
catches is taken in international waters, more than 12 miles offshore.

The Spanish longline fleet operates from the Strait of
Gibraltar (5ºW) to 7ºE near Sardinia, and from 42ºN to the
Algerian coast (Camiñas and De la Serna, 1995). In the early 1990s a
Spanish fleet of 30 longlines operated throughout the year in the southwestern
Mediterranean. In the summer months, when the swordfish fishery peaks, the
number of Spanish boats rose to 60-80. This local fishing effort was
complemented by about 30 Japanese and 30 FoG longliners (Aguilar, Mas and
Pastor, 1992). Overall, some 145 Spanish longliners target swordfish in
Mediterranean waters and a further 100 artisanal boats operate in coastal waters
during the summer. Seventy percent of total yearly effort in this fishery is
concentrated in the summer and autumn. Bycatch, excluding turtles, accounts for
10% of total landings in weight (Camiñas and De la Serna,
1995).

Italian longlining fleets targeting swordfish and albacore are
based mostly in Sicily, Puglia, Sardinia, Campania and Liguria, and comprise
more than 1 500 boats operating mainly in the Gulf of Taranto, the south
Adriatic and the Aegean Sea (Camiñas and De la Serna, 1995). About 27
longline units operated in 1997 in the vicinity of the Santuario dei Cetaceii,
in the Western Central Ligurian Sea, where driftnets have been banned since
1992. These fleets, however, are able to reach much more distant grounds. In
1992, the Sicilian fleet operated from Crete and Cyprus in waters close to Egypt
and the rest of the north African coast (Cavallaro and Luca, 1996). Italian
longline fleets are also known to reach Iberian waters during the autumn. In the
central southern Tyrrhenian Sea, swordfish have historically been fished with
driftnets (spadara) but an important longline fishery has recently
been established at Mazzara del Vallo in the Strait of Sicily (Di Natale et
al., 1996).

The Greek National Statistic Service includes longlining in
the broad category of coastal fisheries and although no specific
figures are available, it is estimated that the swordfish fishery accounts for
more than 50% of the total professional fishing effort by Greek fleets in
western Greece (Panou et al., 1999). A total of 47 longline boats were
known to be based in the Ionian Islands and the Epirus coastal region alone in
the mid-1980s. Camiñas and De la Serna (1995) gave a total figure of 400
boats from 70 ports being involved in the Greek swordfish fishery in 1991. The
main fleets, concentrating 50% of total Greek production, are based in Kalymos
(south-east Aegean) and Chania (Crete). Of the total annual catch, 70% is taken
at the peak of the season, from May to September, in an area covering the Aegean
Sea, the Ionian Sea and even the Levant Sea. About 180 vessels are involved in
albacore fishing in the central and northern Adriatic.

3.2.3 Size selectivity of surface
longlining regarding the target species

Seasonal differences in the size of swordfish caught by the
Spanish longline fleet operating in the Mediterranean have been reported,
suggesting that different age groups are targeted in different seasons
(Camiñas and De la Serna, 1995). Smaller specimens are caught during the
autumn months, when fishing is carried out in more coastal areas, peninsular and
insular (for the Balearic Is.). The Italian longline fleet is also known to
operate near the coast in the Strait of Sicily during the autumn (Di Natale
et al., 1996). In Greek waters, however, the fishing of swordfish is
prohibited by law from October to January (Panou et al., 1999).

The selectivity of longline fishing in the Mediterranean with
respect to ICCATs minimum legal sizes for swordfish and bluefin tuna are a
matter of concern. The percentage of legally undersized swordfish with respect
to current EU legislation (< 120 cm LJFL) caught by Spanish longliners in the
Mediterranean was 81-83% in 1992-1994 (Anonymous, 1995, cited in Raymakers and
Lynham, 1999). A recent study commissioned by TRAFFIC and WWF confirmed the
previous figures, and demonstrated the Spanish longline fleets' non-compliance
with its international and EU legal obligations (Raymakers and Lynham, 1999).
The study, based on observers at the main Mediterranean Spanish ports from June
to September 1998, showed that 86% of a sample of 2 097 swordfish landed from
171 vessels had been illegally fished (<120 cm., and probably <25 kg).
This sample represented about 7.5% of the 1991-1995 annual average of swordfish
caught by Spanish fleets in the Mediterranean. As for bluefin tuna, 210 out of a
sample of 254 individuals (or 83% of the total) landed by ten longline vessels
were below the minimum legal size of 6.4 kg. The monitoring of swordfish catches
by the Italian longlining fleet operating in the central and southern Tyrrhenian
Sea and the Strait of Sicily also pointed to the predominance of immature,
small-sized individuals in this fishery (Di Natale et al., 1996). The
mean weights of individuals caught in the southern and central Tyrrhenian Sea
were 16.8 kg and 12 kg respectively, and 17.5 kg in Sicily. These values
contrast sharply with the current minimum weight of 25 kg recommended by
ICCAT.

Albacore longlining also has negative consequences on
swordfish and bluefin tuna populations. Di Natale et al. (1996) report
small-hooked surface longlines targeting albacore in western Italian waters
catching very small swordfish, weighing less than 3 kg. De Metrio et al.
(1997) investigated the catches of the albacore longline fleets operating in
1995 in the Gulf of Taranto (north Ionian Sea), the eastern coast of Sicily
(south Ionian) and the north Sicilian coast (south Tyrrhenian), an area fished
by a fleet of nearly 150 vessels. Comparisons of landings at ports and catches
on board revealed that most swordfish catches were not reported at the ports.
Catches of young (class 0) swordfish and bluefin tuna were estimated at 53.2%
and 10.1%, respectively, of the total catch in number of individuals, which
point to high absolute catches.

3.2.4 Conclusions

Apart from harming important groups taken as bycatch, pelagic
longlining in Mediterranean waters is clearly unselective with respect to
non-target undersized fractions of the populations that are the object of the
fishery. Some data even point to immature large pelagic fish being the bulk of
surface longline fisheries. This applies mainly to swordfish and, to a lesser
extent, bluefin tuna. Regardless of whether small specimens are caught because
of the intrinsic action of the gears or merely reflect overfishing of
populations, known to be at low levels, action could be undertaken to minimize
the negative impact of present longline practices. The creation of no-fishing
zones in strategic areas and seasons, for example spawning and nursery grounds
or coastal areas in autumn, could be considered as recommended also by the
authors of the TRAFFIC-WWF study. The extension of the Spanish fisheries
jurisdiction to a vast region in the western Mediterranean (Royal Decree
1315/1997) provides an opportunity to enforce EU Regulations (derived from ICCAT
Recommendations) and implement other new measures in these former international
waters.

This section does not set out to deal with the issue of the
monospecific management of large pelagic populations, but it is clear that
pelagic longlining in the Mediterranean induces high levels of mortality in
several ecologically valuable and biologically vulnerable species as well as in
non-target, legally protected fractions of swordfish and tuna populations, to
the extent that the fishery might just as well be targeting this latter group.
Large pelagic species are apex predators and key players in Mediterranean
pelagic ecosystems and their conservation appears to be essential to keep
ecosystems healthy. Overfishing of pelagic apex predators (bonito and mackerel)
in the Black Sea may have triggered a trophic cascade effect working down to
lower trophic levels, making the system less resilient to external changes
(Daskalov, 1999). The well-known Mnemiopsis invasion led to the collapse
of fisheries in the late 1980s. All the evidence strongly suggests that current
policies should be revised in favour of an ecosystem-based management of large
pelagic fisheries and the related surface longlining fishing
practices.

3.3 The ecosystem impact of artisanal
gears

3.3.1
Introduction

The diversity and economic importance of artisanal gears in
small-scale fisheries are essential features of Mediterranean fishing. Stergiou,
Petrakis and Politou (1996) consider that small-scale fishing is
socioeconomically more important than trawling and purse seining in Greece since
it occupies 87.5% of all boats, 57.5% of total fishing power (in HP) and
produces near half of the total wholesale value of catch. The heterogeneity of
gears and target species makes it difficult to reach any general conclusions as
to the impact of these small-scale practices on the ecosystem. Factors such as
the season of the year, the characteristics of the area exploited (depth, type
of bottom, etc.) further complicate the picture. Some trends emerge nonetheless,
such as the higher selectivity of some gears and the negative effects of other
artisanal practices. Ghost fishing by abandoned or discarded small-scale gears
is another issue of potential importance in the Mediterranean. These points are
discussed below, excluding the specific effect of some small-scale fisheries on
the populations of endangered species such as monk seals or turtles addressed in
previous sections.

3.3.2 Overview

Static nets are usually highly selective, catching larger fish
than, in most cases, trained nets. Different types of nets can, in turn, also
differ deeply as to intra- and interspecific selectivity. A comparative study of
catches in eight types of net gear (both beach seines and static gill and
trammel nets) in the Aegean Sea revealed that large meshed trammel nets yielded
the biggest commercial catches as a proportion of total catches (Stergiou,
Petrakis and Politou, 1996). In another study, the relative selectivity of
trawlnets, bottom longlines and gillnets operating on slope bottoms (between
200-700 m) in the Southern Adriatic Sea was analysed with respect to three
demersal species: blackmouth catshark (Galeus melastomus), rockfish
(Helicolenus dactylopterus) and blue whiting (Micromesistius
poutassou) (Ungaro et al., 1999). The results showed that gillnets
(rete ad imbrocco) were always the most positive selective gear for
size of individuals caught. The modal length of blackmouth catshark caught by
gillnets, for instance, was 54 cm, contrasting sharply with only 16 cm reported
for trawlnets. Sbrana et al. (1999) carried out a comparative study of
interspecific selectivity with three kinds of static nets: monofilament
gillnets, trammel nets with a monofilament inner panel and entirely
multifilament trammel nets, and also tested the effect of different mesh sizes.
The study concluded that whereas the number of species caught was negatively
correlated with mesh size of a given gear type, inter-specific selectivity
decreased from gillnets to trammel nets; the trammel nets with three
multifilament nets were the least selective of all. However, the target species
in the Sardinian cuttlefish (Seppia officinalis) fishery using trammel
nets constituted up to 78% of the total catch weight (Cuccu et al.,
1999).

Beach seines, deployed in very shallow grounds to catch small
fish, are common in some Mediterranean waters and are relatively unselective.
They are used in Italy, where they are known as sciabica, and other
countries to catch small sardine fry (biancheto), transparent goby
(Aphia minuta) (rosetto) and sand eel (Gymnammodytes
cicerellus) (cicerello). The beach seine fleet in Crotone
(northwestern Ionian Sea) operates on bottoms less than 9 m deep (Carbonara
et al., 1999). A different kind of beach seine (sonsera) is
used to catch sand eel in a limited area off the coast of northern Catalonia
(northwestern Mediterranean). Fine-meshed trawling gears are employed in
Adriatic waters mainly in the Gulf of Manfredonia (Casavola, De Ruggieri and Lo
Caputo, 1999). The transparent goby fishery is allowed to operate there from
January to March, and catches mainly Aphia minuta (53.7%) and small
sardine (39.7%), together with other fish (including juvenile anchovy) and
benthic invertebrates (Casavola et al., 1999). The Sardinian squid
(Loligo vulgaris) fishery works with beach seines on shallow bottoms
ranging from 25 m deep almost to the shore. Whereas squid catches consist of
adult individuals, contrasting with the local trawlnet catches, Loligo
vulgaris accounts for only 20% of the total catch in weight and salema
(Sarpa salpa) makes up the bulk of the catch (72%) (Cuccu et al.,
1999). A comparative study of small-scale gears used in the south Euboikos Gulf
(Greece) during 1992 and 1993 revealed that beach seines were very effective in
catching younger and smaller specimens, leading the authors to conclude that
banning of beach seines is essential for the conservation of demersal and
inshore diversity (Stergiou, Petrakis and Politou, 1996). It is worth
mentioning that the minimum legal beach seine cod-end mesh size in Greek waters
is only 8-mm bar length.

Game fishing is a growing leisure activity in many
Mediterranean waters, and probably has a significant impact on some species, for
example bluefin tuna and swordfish, whose low age classes suffer particularly.
As many as 380 000 juvenile swordfish are estimated to be caught annually by
non-commercial fishermen in Calabria (De Metrio et al., 1997). The impact
of this activity on marine populations and ecosystems in the Mediterranean
remains to be adequately addressed.

The massive use of fixed nets (and other artisanal gears such
as traps) in many small-scale Mediterranean fisheries, makes ghost fishing by
abandoned or discarded gears a potentially important problem in Mediterranean
waters but has attracted scant attention. Erzini et al. (1997) carried
out an experimental study of gillnet and trammel net ghost fishing in shallow
(15-18 m) rocky bottoms in the Atlantic waters off the coast of the Algarve in
southern Portugal. The results of the study indicated that abandoned gillnets
yielded more catches than trammel nets as measured by the mean number of fish
caught by 100 m-length pieces of nets after 120 days of deployment on the bottom
(gillnets: 344 fish specimens entangled; trammel nets: 221 fishes entrapped).
Whilst catches decreased gradually over time, nets continued to catch fish four
months after the experiments had started. Osteichthyes were the most numerous
group among the 39 species recorded, accounting for 88.8% of the total specimens
in number. The other groups included molluscs, gastropods and crustaceans.
Sparidae species, however, made up about 33% of total catches in numbers. There
is evidence suggesting that nets lost in deep water may have an even longer
effective fishing life span, running to years. This is matter of concern since
some deep gillnet fisheries (such as the Italian rete ad imbrocco in
the southern Adriatic) operate in Mediterranean waters.

The results of the study mentioned above also implicated ghost
fishing in disturbing demersal food-webs in a similar way to that reported for
trawl discards. The authors described considerable scavenging pressure on
entrapped fish by octopuses, cuttlefish, conger eels, moray eels and wrasses
(Coris julis), which could have led to an underestimate for the actual
fishing capacity of discarded nets.

3.3.3 Conclusions

The high diversity of artisanal gears (and species targeted)
and the importance of small-scale fisheries in many Mediterranean coastal waters
introduce considerable additional complexity to the overall issue of the
ecosystem-based management of Mediterranean fisheries. In this context,
Stergiou, Petrakis and Politou (1996), referring to Greek small-scale fisheries,
stated that management strategies based on single species calculations
will be of limited value, and advocated the promising alternative approach
of a management regime based on marine harvest refuges. This holistic approach
overcomes, in part, the problems related to the variable intraspecific and
interspecific selectivity of different gears and other variable factors such as
bottom type, depth of setting, seasons and the phenomenon of ghost
fishing.

There is enough scientific consensus to support the total
banning of some artisanal gears in Mediterranean waters. Beach seines should be
eradicated from EU Mediterranean waters from January 2002. All fishing with
coastal seines will also be prohibited by 2001 in Turkish Aegean waters, as long
demanded by many local artisanal fishermen (Anonymous, 1999b). Game fishing is a
superfluous non-commercial practice and must be prevented from inflicting any
additional damage on vulnerable species such as swordfish and bluefin
tuna.

In general terms, and leaving managerial issues aside, many
artisanal fisheries (such as static or bottom longlines) are probably more
selective than trawling practices, and therefore a preferable, much less
ecosystem-impacting alternative, provided that discarding gears at sea can be
stopped.

3.4 The case of Mediterranean driftnet
fisheries

3.4.1
Introduction

The outstanding impact of bycatches by surface swordfish
driftnets fleets on many vulnerable groups inhabiting Mediterranean waters, as
reported in some detail in previous sections, makes a summary of the present
status of these fleets desirable. Details of technical aspects of gears and
specific fleets are not included here, since the controversial issue of
driftnets has been extensively discussed and an extensive literature is already
available (see Paul, 1994, for a global, world-wide account of this
issue).

3.4.2 State of the
art

The Italian Mediterranean driftnet fleet of at least 650
vessels in 1996, using nets measuring on average 10-12 km long, has long been at
the centre of the debate, though it is not the only one operating in
Mediterranean waters. Driftnet fleets continue their activities despite
successive international initiatives banning or limiting this low selective
fishing practice (swordfish represented only 18% of the Italian driftnet catch
in numbers, but nearly 50% in weight; Di Natale, 1996). Resolutions 44/225 and
46/215 adopted in 1989 and 1991 by the General Assembly of the United Nations
recommended the imposition of a moratorium on all large-scale pelagic driftnet
fishing by 30 June 1992. European Regulation (EC) No 345/92 prohibited driftnet
fishing in the Mediterranean with nets more than 2.5 km in length, as did the
General Fisheries Commission for the Mediterranean (GFCM) in 1997 under
Resolution 97/1, a binding recommendation. Effective moves to restructure the
Italian driftnet fleet have been made since the adoption of European Regulation
(EC) No 1239/98 and later regulations totally banning the use of driftnets by
Community fishing vessels within and outside Community waters from 1 January
2002. Finally, in November 2003 ICCAT laid down a binding Recommendation (03-04)
completely banning the use of driftnets for fisheries of large pelagics in the
Mediterranean.

Some fleets indeed limited driftnet fishing in Mediterranean
waters during this long political process, whilst others grew rapidly. The
Spanish Mediterranean swordfish driftnet fleet is an example of the former. In
1993-1994, 27 boats illegally deployed nets 3-5 km long on the Mediterranean
side of the Gibraltar Straits (Silvani, Gazo and Aguilar, 1999). This fishery
was particularly unselective, with swordfish catches accounting for only 5-7% of
total catch in numbers, which was mostly sunfish (Mola mola) (71-93%) and
other species such as dolphins and turtles (see the respective sections above).
After 1994, these boats stopped using large-scale driftnets and changed target
species. Other fleets, on the contrary, have continued to expand, in some cases
taking advantage of gears supplied from reconverted fleets. This is the case of
North African countries and Turkey, despite national legislation banning
large-scale swordfish driftnetting in most of them. Italian and Greek fishermen
are known to sell their equipment to Turkish fishermen (A.C. Gücü,
pers. comm.). According to Tudela et al. (2005) at least 177 Moroccan
vessels carry out large-scale driftnet activities in the Alboran Sea and Straits
of Gibraltar areas (357 according to Moroccan sources; document ICCAT
SCRS/2002/139). In addition to this important North African fleet, the other
major fleets involved are Italian (about 90-100 vessels still exist), Turkish
(45-110 vessels; Akyol et al., 2003, SCRS/ICCAT, 2001) and French (46-75;
SGFEN/STECF, 2001). Many evidences point to other countries like Algeria as
being also likely driftnetters, though confirmed official information is not
available.

Solid legal instruments already exist to tackle the issue of
driftnet fishing in the Mediterranean, especially after the recent total ban
issued by ICCAT. Their enforcement should be a priority for the different
coastal states and the concerned Regional Fisheries Organizations (GFCM and
ICCAT).